On Sat, Sep 27, 2014 at 12:16 PM, Al Viro [off-list ref] wrote:

FWIW, I suspect that the right approach is to put refcount + rcu_head in
front of external name and do the following:

That's actually fancier than I was expecting. I was just thinking
doing a whole new allocation and freeing the old one using RCU. But I
guess you're right, you do need the rcu_head even for that, and once
you start adding fields you might as well just add a refcount too, and
then you don't have the annoyance of a potential memory allocation in
that code.

So your approach is better and doesn't sound too painful at all.

But yeah, I guess we can/should do the trivial ugly thing for 3.17.
Send me a proper pull-request,

                  Linus